Final answer:
Lithium has one valence electron in its outer shell.
Step-by-step explanation:
Lithium (Li), which has an atomic number of 3, has three electrons. Two of these electrons occupy the first electron shell, while the third electron fills the second electron shell. The second electron shell can hold a maximum of eight electrons. Elements in the second row of the periodic table, from lithium to neon, all have two electron shells. Atoms with more than ten electrons require additional electron shells found in the third and subsequent rows of the periodic table. Therefore, lithium has one valence electron in its outer shell.